A CMOS microcoil-associated preamplifier for NMR spectroscopy

Abstract

For improving sensitivity of nuclear magnetic resonance (NMR) measurements, an in-field preamplifier in a low-cost CMOS process is presented. It is based on a second-generation positive current conveyor (CCII+), with an impedance-matching output stage. The circuit has been designed with optimization of key performances, such as bandwidth, noise, and offset voltage. There have also been precautions taken against potential effect of strong magnetic field under which the circuit should operate. The designed preamplifier has a voltage gain of 15 dB and a bandwidth of 100 MHz. After fabrication of the circuit, we have carried out testing work, including in-field circuit test and characterization of MOS transistors. Under 2-T magnetic field, there have not been substantial changes in overall circuit performances compared to results obtained by post-layout simulations. For an experiment of NMR measurements with and without in-field preamplifier, the circuit is coupled with a receiver micro-coil. The experiment has been to detect protons at 85.13-MHz resonance frequency under 2-T magnetic field with water sample. The obtained results have shown a 14-dB signal-to-noise ratio improvement when the preamplifier is associated with the receiver coil.Index Terms-Current conveyor, in-field preamplifier, nuclear magnetic resonance (NMR) active probe, receiver micro-coil.

A broadband single-chip transceiver for multi-nuclear NMR probes

“…The design of electronic micro-chips for NMR purposes has the aim to shrink the size of electronics for low-cost NMR spectrometers [16][17][18][19] and to combine microcoils with integrated receivers in order to achieve probes parallelization and high spin sensitivity. [20][21][22][23] The first integrated probe was proposed for magnetometry purposes and employed integrated pick-up-coils coupled to receivers, with the excitation operated by a second inductively decoupled coil. 24 Receiver-only chips, with the whole electronics buried below integrated microcoils, were proposed a) marco.grisi@epfl.ch as optimal choice for micro-imaging, 23 parallel imaging arrays, 20 and probes for surgical guidance.…”

A single-chip array of NMR receivers

“…In this paper, we propose the use of an inexpensive standard complementary metal-oxide-semiconductor (CMOS) technology to build large receiver arrays with good performance. Recently, there have been other attempts that exploit integrated electronics for NMR applications: Reception coil and receiver electronics were placed on the same IC to form a single receiver for NMR magnetometry [21]; external coils were combined with CMOS chips to form hybrid systems for magnetometry [22] and NMR-spectroscopy [23]; and, chips with a high level of integration were combined with external coils to perform very specific tasks such as spectral scanning MRI [24] or to form more complex systems for biomolecular sensing [25]. Our attempt is the first array of receivers with integrated electronics and reception coils co-integrated on the same IC.…”

Integrated active tracking detector for MRI‐guided interventions

“…Recently, several NMR probes based on complementary metal oxide semiconductor integrated circuit (CMOS) technologies have been reported (17–23). In this work, a standard CMOS is used to realize an active tracking device, which in our approach consists of a microcoil and receiver electronics integrated onto a single silicon chip of less than 2 mm 3 .…”